1. Field of the Invention
The present invention relates to a golf club head.
2. Description of the Related Art
The face of a golf club head include a plurality of grooves, known as marking lines, score lines, or face line grooves (hereinafter referred to as score line grooves), which affect the spin amount on a ball. It is desirable to have the grooves on an iron club head, especially a wedge, in order to increase the spin amount on the ball. The surface roughness of the face also influences the spin amount of a ball.
Japanese Patent Laid-Open No. 9-192274 discloses a golf club having score line grooves of V-shaped or trapezoidal cross section. Japanese Patent Laid-Open No. 9-70457 and No. 10-179824 disclose a golf club head having score line grooves edges (boundary portions between side surfaces of the grooves and a face) of which are rounded. This rounding has an effect of preventing a golf ball from getting damaged (for example, scratches and the like). Japanese Patent Laid-Open No. 2003-93560 and No. 2005-287534 disclose a golf club head having score line grooves each of which has a side surface formed not by a single surface, but by two differently angled surfaces. In Japanese Patent No. 3463779, a set of iron type golf clubs each of which has an area ratio of the score line grooves to the face set differently depending on its own type number of golf clubs is disclosed. Incidentally, a golf club head used in the official games is subject to constraints on a width and depth of the groove, and a pitch between the adjacent grooves specified in the rules, and therefore, in consideration of applications in the official games, it is required to design a golf club head in a range to meet the rules.
The surface roughness of the face also influences the spin amount of a ball. Japanese Patent Laid-Open No. 2005-169129 discloses a golf club head in which the surface roughness of the face is set to 40 Ra or more. Japanese Patent No. 3000921 discloses a golf club head in which a plurality of fine grooves are formed on the face in addition to the score line grooves. Incidentally, the surface roughness of the face of a golf club head for official competitions is also restricted by rules. Therefore, when an application in official competitions is considered, a golf club head needs to be designed within a range conforming to the rules.
Now, a spin amount of a golf ball in the rain or hitting a shot in the rough tends to be smaller than that with out the rain or hitting on the fairway. A method for prevention of a decrease in the spin amount of a ball includes sharpening the angle of a groove edge. However, a decrease in the angle of the groove edge may cause a ball to be easily damaged. Damage to the ball can be decreased by rounding the edges of the grooves as the golf club head disclosed in Japanese Patent Laid-Open Nos. 9-70457 and 10-179824. In this case, however, the spin amount of the ball also decreases.